Wind power is widely accepted as an environmental friendly means for producing electric power. Unfortunately, wind generators available today use large and expensive turbine generators mounted at a fixed position on the end of a large vertically aligned pole or tower.
Wind power must compete with and be cost efficient relative to hydro-electric generator systems, coal electric power generator systems, solar and nuclear power electrical power systems. Unfortunately today, the costs of rotors, blades, the generators, the nacelles, the electronics, the towers, and the footings and the installation costs are very high. In addition, the generation of noise, vibrations, visibility of the tower, the impact on birds, and the debris field if a catastrophic event occurs, are also important factors that impede wind power usage.
It is well known, that hills, valleys, trees and buildings affect the velocity of the wind, the wind's direction and turbulence. Most wind power systems are setup and operated in open rural regions with little or no obstructions and few nearby neighbors. The systems include large nacelles with large hub assemblies. The hub assemblies are specifically designed for use with two to three long solid blades. The nacelles and hub assemblies are mounted on the end of a tower that holds the hub assemblies a sufficient elevation above the ground to allow the hub assemblies to rotate freely in the wind.
Large wind power systems found in the prior art typically use high RPM, low torque synchronous generators the produce electricity when the sustainable winds are within a narrow range of velocities. Because such generators require high input shaft velocities, gear boxes are often used between the hubs and the generators. When the velocity of the wind is below the wind range, the hub assemblies or gear boxes are disconnected from the generators. When the wind velocity is above the range, the blades are furled to allow the wind to reduce lift and prevent excessive rotation. In high velocity winds, a dynamic brake may be applied to the hub, gear box or generator to reduce or stop rotation.
High torque, low RPM asynchronous generators produce electricity at lower RPMs. The electricity produced by asynchronous generators is determined by generator shaft's RPMs and the amount of torque applied to the shaft. The shaft's RPMs and the torque are determined by the number of blades and the surface area of each blade. Unfortunately, the solid blades commonly used with wind generator systems are suitable for use with asynchronous generators because of their relatively long lengths and relatively high moments of inertia.
The swept area is the area of a circle the blades of a wind generator create when rotating. The greater the swept area, the greater energy can be captured from the wind and the more electrical energy can be produced.
The power produced by the rotor on a wind generator system, is the product of shaft RPM speed and torque. To transfer equal power, a rotating shaft can operate either at high speeds and low torque, or at low speeds and high torque. As the blades on a rotor increase in size, their RPM speed decrease and the torque increases. Conversely, as the blades on a rotor decrease in size, their RPM speed increase and the torque decreases.
Most wind power systems use synchronous, high RPM, low torque generators to produce A.C. or D.C. electric current. A gear box is normally coupled to the rotor to generate a sufficiently high RPM's needed to rotate the generator. The speed of the generator remains relatively constant as the wind fluctuates. Unfortunately, gear boxes are heavy components that substantially increase the purchase price, maintenance costs and installation costs.
Less common and less expensive wind power system use asynchronous, low RPM, high torque generators to produce A.C. or D.C. electric current. The generators are normally directly connected to the rotors. Because the wind speed can vary, the speed of the asynchronous generator and its output vary with the wind speed. Asynchronous generators are induction generators that require a specific amount of torque applied by the wind to the blades on the rotor. The greater the wind speed, the greater the rotor's RPM's and greater the torque applied to the rotor.
What is needed is a wind generator with an universal hub that uses different qualities and sizes of lightweight blades that can be used in low to moderate winds and in turbulent and non-turbulent winds. What is also needed is such wind generator and universal hub that can be used with either a synchronous or asynchronous generator. What is needed is a wind generator the use blades designed to rotate in low or moderate winds, and respond quickly to changes in the wind speed. What is needed is a blade that automatically releases its engagement or capture of the wind when the wind exceeds a predetermined speed. What is needed is a wind generator system that uses blades that are lightweight and cause little or minimal damage when released. What is needed is a wind generators that can be used with shorter towers and with slowly rotating rotors thereby reducing environmental damage or concerns.